Question 913201
p = .1, n = 6
1) P(x = 0) = binompdf(6, .1, 0) 0r (.9)^6
2) P(x = 5 or 6 defective pens) = binompdf(6, .1, 5) + binompdf(6, .1, 6)
3) P(Less than 3 defective pens) = binomcdf(6, .1, 2)
..........
Or by hand Using 
{{{P (x)= highlight_green(nCx)(p^x)(q)^(n-x) }}} 
p and q are the probabilities of success and failure respectively. 
In this case p = .1 & q  = .9 , n = 6
{{{nCx = (n!)/x!(n - x)!)}}} 
............For ex
3) P(Less than 3 defective pens) = P(0) + P(1)+ P(2)